It is known in the art to provide a diesel engine with an exhaust treatment system that includes one or more particulate traps or filters that are operative to filter out and collect particulates from the exhaust gas stream discharged from the engine. Such particulates consist largely of carbon particles that tend to plug the filter, thus restricting exhaust gas flow therethrough. Accordingly, after continued use of such a system for a period of time dependent on engine operation, it becomes desirable to effect regeneration of the filter.
Diesel engine exhaust traps are currently being manufactured by Corning and others. The trap is of a ceramic material and is placed in line in series with the exhaust pipe so that all exhaust gases must go through the trap. The trap is constructed such that the gases must pass through a ceramic wall with very small pore size in order to escape to the atmosphere. As the pores become clogged, a backpressure arises upstream of the trap.
Due to manufacturing limitations in the size of ceramic filters, some engine applications require several filters so that the backpressure remains below engine specifications at all engine conditions. As one or more filters become loaded, regeneration must be effected and, consequently, filters being regenerated are bypassed from the exhaust stream and are unavailable for filtering. In some systems, three or more filters may be used. The means of deciding how to load multiple filters, when to regenerate them, and how to best utilize unloaded filters is not a trivial problem. The present invention is directed to a methodology for operation of such a system.